civil 3d 2019 start new drawing text window wont displat
Drawing shapes¶
OpenCV has different cartoon functions to draw:
- lines
- circle
- rectangle
- ellipse
- text
Using Numpy¶
Numpy is a very powerful math module for dealing with multi-dimensional information such every bit vectors and images. The OpenCV images are represented every bit Numpy arrays. At the get-go of a programme we import both:
import cv2 as cv import numpy every bit np To create an empty color paradigm nosotros create a 3D array of zeroes:
img = img = np . zeros (( 100 , 600 , 3 ), np . uint8 ) cv . imshow ( 'RGB' , img ) When zooming, we can meet the iii color components.
To create an empty gray-scale image nosotros create a 2nd array of zeroes:
gray_img = np . zeros (( 100 , 600 ), np . uint8 ) cv . imshow ( 'Greyness' , gray_img ) The grayscale values for each pixel go from 0 to 255. In a black image all pixel values are 0.
import cv2 as cv import numpy every bit np img = img = np . zeros (( 100 , 500 , three ), np . uint8 ) cv . imshow ( 'RGB' , img ) gray_img = np . zeros (( 100 , 500 ), np . uint8 ) cv . imshow ( 'Greyness' , gray_img ) cv . waitKey ( 0 ) cv . destroyAllWindows () draw1.py
Define colors¶
Colors are defined by three base colors: Blue, Light-green and Carmine. All three put to zero gives black, all three at the maximum gives white:
BLACK = ( 0 , 0 , 0 ) WHITE = ( 255 , 255 , 255 ) Different from the more common RGB ordering, OpenCV uses the ordering BGR:
RED = ( 0 , 0 , 255 ) GREEN = ( 0 , 255 , 0 ) Blueish = ( 255 , 0 , 0 ) Mixing color components results in more colors:
CYAN = ( 255 , 255 , 0 ) MAGENTA = ( 255 , 0 , 255 ) YELLOW = ( 0 , 255 , 255 ) Depict a line¶
The office cv.line() adds a line to an image:
cv . line ( epitome , p0 , p1 , color , thickness ) - prototype where the line is added
- first point p0
- end bespeak p1
- line color
- line thickness
Lets define iii points:
p0 = 10 , 10 p1 = 300 , 90 p2 = 500 , 10 Now nosotros can draw 2 colored lines:
cv . line ( img , p0 , p1 , Carmine , 2 ) cv . line ( img , p1 , p2 , Yellow , 5 ) 
If the image is a gray-scale prototype, instead of the color triplet, a grayscale value from 0 (black) to 255 (white) is used:
cv . line ( gray_img , p0 , p1 , 100 , ii ) cv . line ( gray_img , p1 , p2 , 255 , 5 ) 
import cv2 as cv import numpy every bit np RED = ( 0 , 0 , 255 ) Yellow = ( 0 , 255 , 255 ) p0 , p1 , p2 = ( x , 10 ), ( 300 , xc ), ( 400 , 10 ) img = img = np . zeros (( 100 , 500 , iii ), np . uint8 ) cv . line ( img , p0 , p1 , RED , 2 ) cv . line ( img , p1 , p2 , Xanthous , five ) cv . imshow ( 'RGB' , img ) gray_img = np . zeros (( 100 , 500 ), np . uint8 ) cv . line ( gray_img , p0 , p1 , 100 , ii ) cv . line ( gray_img , p1 , p2 , 255 , 5 ) cv . imshow ( 'Gray' , gray_img ) cv . waitKey ( 0 ) cv . destroyAllWindows () line1.py
Select thickness with a trackbar¶
We can use a trackbar to set the thickness of the line. The trackbar callback function has ane statement - the line thickness. Trackbar arguments are e'er integer and they always start at 0. Even so, for lines the smallest line thickness is 1. Therefore we utilise the max function to make the thickness at least ane. To have a numeric feedback, nosotros display the thickness value likewise in the overlay:
def trackbar ( x ): x = max ( 1 , x ) cv . displayOverlay ( 'window' , f 'thickness= {x} ' ) Next we have to redraw the line. Nosotros get-go past resetting the image to 0. And so we describe the line and display the new image:
img [:] = 0 cv . line ( img , p0 , p1 , RED , x ) cv . imshow ( 'window' , img ) 
# Select line thickness with a trackbar import cv2 every bit cv import numpy as np Blood-red = ( 0 , 0 , 255 ) p0 , p1 = ( 100 , xxx ), ( 400 , 90 ) def trackbar ( x ): 10 = max ( 1 , 10 ) cv . displayOverlay ( 'window' , f 'thickness= {x} ' ) img [:] = 0 cv . line ( img , p0 , p1 , Scarlet , 10 ) cv . imshow ( 'window' , img ) img = np . zeros (( 100 , 500 , 3 ), np . uint8 ) cv . line ( img , p0 , p1 , RED , 2 ) cv . imshow ( 'window' , img ) cv . createTrackbar ( 'thickness' , 'window' , 2 , 20 , trackbar ) cv . waitKey ( 0 ) cv . destroyAllWindows () line2.py
Select color with a trackbar¶
We tin use a trackbar to set the line color. The trackbar is used to select an index into a color listing which we define with 7 colors:
colors = ( Blood-red , Greenish , BLUE , CYAN , MAGENTA , Xanthous , WHITE ) The trackbar is defined to return an integer value from 0 to six:
cv . createTrackbar ( 'color' , 'window' , 0 , 6 , trackbar ) Inside the trackbar callback function nosotros apply the index to look up the color. To requite numeric feedback we brandish the colour RGB value in the overlay:
def trackbar ( x ): colour = colors [ ten ] cv . displayOverlay ( 'window' , f 'colour= {color} ' ) 
# Select line color with a trackbar import cv2 as cv import numpy as np Reddish = ( 0 , 0 , 255 ) GREEN = ( 0 , 255 , 0 ) BLUE = ( 255 , 0 , 0 ) CYAN = ( 255 , 255 , 0 ) MAGENTA = ( 255 , 0 , 255 ) YELLOW = ( 0 , 255 , 255 ) WHITE = ( 255 , 255 , 255 ) colors = ( RED , Light-green , BLUE , CYAN , MAGENTA , Yellow , WHITE ) p0 , p1 = ( 100 , 30 ), ( 400 , ninety ) def trackbar ( x ): colour = colors [ x ] cv . displayOverlay ( 'window' , f 'color= {color} ' ) img [:] = 0 cv . line ( img , p0 , p1 , color , 10 ) cv . imshow ( 'window' , img ) img = np . zeros (( 100 , 500 , 3 ), np . uint8 ) cv . line ( img , p0 , p1 , Ruddy , ten ) cv . imshow ( 'window' , img ) cv . createTrackbar ( 'colour' , 'window' , 0 , six , trackbar ) cv . waitKey ( 0 ) cv . destroyAllWindows () line3.py
Select stop point with the mouse¶
Let's apply the mouse for selecting the stop betoken of the line. The mouse callback function has the x and y coordinates every bit arguments. Nosotros are just interesed in the mouse movement when a button is pressed (flags==1). The current mouse coordinates volition be the new end point for the line. We brandish this coordinates in the overlay:
def mouse ( outcome , 10 , y , flags , param ): if flags == one : p1 = x , y cv . displayOverlay ( 'window' , f 'p1=( {ten} , {y} )' ) 
# Select cease point with the mouse import cv2 as cv import numpy as np GREEN = ( 0 , 255 , 0 ) p0 , p1 = ( 100 , 30 ), ( 400 , xc ) def mouse ( event , x , y , flags , param ): if flags == 1 : p1 = x , y cv . displayOverlay ( 'window' , f 'p1=( {x} , {y} )' ) img [:] = 0 cv . line ( img , p0 , p1 , GREEN , ten ) cv . imshow ( 'window' , img ) img = np . zeros (( 100 , 500 , 3 ), np . uint8 ) cv . line ( img , p0 , p1 , GREEN , 10 ) cv . imshow ( 'window' , img ) cv . setMouseCallback ( 'window' , mouse ) cv . waitKey ( 0 ) cv . destroyAllWindows () line4.py
Draw a complete line¶
Let's now draw a complete line with the mouse. At present nosotros need to distinguish betwixt mouse down, mouse motion and mouse up events. When the mouse is down, we start a new line and set both points p0 and p1 to the current mouse position:
if event == cv . EVENT_LBUTTONDOWN : p0 = x , y p1 = 10 , y If the mouse moves (with the button pressed) or if the mouse button goes up, nosotros only ready p1 to the new mouse position:
elif event == cv . EVENT_MOUSEMOVE and flags == 1 : p1 = 10 , y elif issue == cv . EVENT_LBUTTONUP : p1 = x , y At the cease of the mouse callback role nosotros reset the epitome to nil (black), draw the line, display the new paradigm and show the 2 points in the overlay:
img [:] = 0 cv . line ( img , p0 , p1 , RED , x ) cv . imshow ( 'window' , img ) cv . displayOverlay ( 'window' , f 'p0= {p0} , p1= {p1} ' ) 
# Depict a complete line with the mouse import cv2 as cv import numpy as np Crimson = ( 0 , 0 , 255 ) p0 , p1 = ( 100 , 30 ), ( 400 , ninety ) def mouse ( result , x , y , flags , param ): global p0 , p1 if event == cv . EVENT_LBUTTONDOWN : p0 = x , y p1 = x , y elif event == cv . EVENT_MOUSEMOVE and flags == i : p1 = x , y elif event == cv . EVENT_LBUTTONUP : p1 = x , y img [:] = 0 cv . line ( img , p0 , p1 , Scarlet , x ) cv . imshow ( 'window' , img ) cv . displayOverlay ( 'window' , f 'p0= {p0} , p1= {p1} ' ) img = np . zeros (( 100 , 500 , 3 ), np . uint8 ) cv . imshow ( 'window' , img ) cv . setMouseCallback ( 'window' , mouse ) cv . waitKey ( 0 ) cv . destroyAllWindows () line5.py
Draw multiple lines¶
How do we do to draw multiple lines to an image? Kickoff we need to accept a temporary copy img0 which contains the lines of the previous stage of the drawing:
img0 = np . zeros (( 100 , 500 , 3 ), np . uint8 ) img = img0 . re-create () When the mouse push button is downward, we set the two points p0 and p1 to the current mouse position:
if effect == cv . EVENT_LBUTTONDOWN : p0 = x , y p1 = 10 , y When the mouse moves, we reset the current image to the previous image img0 and draw a blue line of thickness ii:
elif event == cv . EVENT_MOUSEMOVE and flags == 1 : p1 = 10 , y img [:] = img0 cv . line ( img , p0 , p1 , BLUE , two ) When the mouse goes up, we reset the image to the previous image img0 , depict a red line of thickness 4, and save this new paradigm every bit img0 :
elif consequence == cv . EVENT_LBUTTONUP : img [:] = img0 cv . line ( img , p0 , p1 , RED , 4 ) img0 [:] = img 
# Draw multiple lines with the mouse import cv2 as cv import numpy equally np Ruby = ( 0 , 0 , 255 ) BLUE = ( 255 , 0 , 0 ) p0 , p1 = ( 100 , 30 ), ( 400 , xc ) def mouse ( consequence , x , y , flags , param ): global p0 , p1 if issue == cv . EVENT_LBUTTONDOWN : p0 = x , y p1 = ten , y elif event == cv . EVENT_MOUSEMOVE and flags == 1 : p1 = x , y img [:] = img0 cv . line ( img , p0 , p1 , Blue , 2 ) elif event == cv . EVENT_LBUTTONUP : img [:] = img0 cv . line ( img , p0 , p1 , Scarlet , four ) img0 [:] = img cv . imshow ( 'window' , img ) cv . displayOverlay ( 'window' , f 'p0= {p0} , p1= {p1} ' ) img0 = np . zeros (( 100 , 500 , 3 ), np . uint8 ) img = img0 . copy () cv . imshow ( 'window' , img ) cv . setMouseCallback ( 'window' , mouse ) cv . waitKey ( 0 ) cv . destroyAllWindows () line6.py
Describe a rectangle¶
The function cv.rectangle() adds a rectangle to an epitome:
cv . rectangle ( prototype , p0 , p1 , colour , thickness ) - paradigm where the rectangle is added
- corner bespeak p0
- corner point p1
- ouline color
- line thickness
If the line thickness is negative or cv.FILLED the rectangle is filled:
cv . rectangle ( img , p0 , p1 , BLUE , 2 ) cv . rectangle ( img , p2 , p3 , Green , cv . FILLED ) 
import cv2 every bit cv import numpy as np BLACK = ( 0 , 0 , 0 ) WHITE = ( 255 , 255 , 255 ) RED = ( 0 , 0 , 255 ) Dark-green = ( 0 , 255 , 0 ) BLUE = ( 255 , 0 , 0 ) CYAN = ( 255 , 255 , 0 ) MAGENTA = ( 255 , 0 , 255 ) Xanthous = ( 0 , 255 , 255 ) p0 = 100 , 10 p1 = 200 , 90 p2 = 300 , 20 p3 = 450 , eighty img = img = np . zeros (( 100 , 500 , 3 ), np . uint8 ) cv . rectangle ( img , p0 , p1 , Blueish , two ) cv . rectangle ( img , p2 , p3 , Dark-green , cv . FILLED ) cv . imshow ( 'RGB' , img ) cv . waitKey ( 0 ) cv . destroyAllWindows () rect1.py
Draw multiple rectangles¶
Now we combine thickness and color trackbar as welle as the mouse callback to create multple rectangles.
import cv2 as cv import numpy as np from draw import * def draw ( x ): global p0 , p1 d = cv . getTrackbarPos ( 'thickness' , 'window' ) d = - 1 if d == 0 else d i = cv . getTrackbarPos ( 'colour' , 'window' ) color = colors [ i ] img [:] = img0 cv . rectangle ( img , p0 , p1 , color , d ) cv . imshow ( 'window' , img ) text = f 'color= {colour} , thickness= {d} ' cv . displayOverlay ( 'window' , text ) def mouse ( event , x , y , flags , param ): global p0 , p1 if issue == cv . EVENT_LBUTTONDOWN : img0 [:] = img p0 = x , y elif event == cv . EVENT_MOUSEMOVE and flags == 1 : p1 = 10 , y elif event == cv . EVENT_LBUTTONUP : p1 = x , y draw ( 0 ) cv . setMouseCallback ( 'window' , mouse ) cv . createTrackbar ( 'colour' , 'window' , 0 , half dozen , depict ) cv . createTrackbar ( 'thickness' , 'window' , 0 , 10 , draw ) cv . waitKey ( 0 ) cv . destroyAllWindows () rect2.py
The common code such as color definitions and image cosmos has been placed in a separate file.
import numpy equally np import cv2 equally cv Blackness = ( 0 , 0 , 0 ) WHITE = ( 255 , 255 , 255 ) Reddish = ( 0 , 0 , 255 ) GREEN = ( 0 , 255 , 0 ) BLUE = ( 255 , 0 , 0 ) CYAN = ( 255 , 255 , 0 ) MAGENTA = ( 255 , 0 , 255 ) YELLOW = ( 0 , 255 , 255 ) colors = ( Blood-red , Light-green , BLUE , MAGENTA , CYAN , YELLOW , WHITE ) p0 = p1 = 0 , 0 img0 = np . zeros (( 200 , 500 , 3 ), np . uint8 ) img = img0 . copy () cv . imshow ( 'window' , img ) describe.py
Describe an ellipse¶
The function cv.ellipes() adds an ellipse to an image:
cv . ellipse ( img , center , axes , angle , a0 , a1 , colour , thickness ) - epitome where the ellipse is added
- centre point
- the 2 axes
- the axis orientation angle
- the get-go bending a0
- the ending angle a1
- ouline colour
- line thickness
import cv2 as cv import numpy every bit np BLUE = ( 255 , 0 , 0 ) center = 200 , 50 axes = 100 , 30 angle = 15 img = img = np . zeros (( 100 , 500 , 3 ), np . uint8 ) cv . ellipse ( img , center , axes , angle , 0 , 360 , Blueish , 2 ) cv . imshow ( 'RGB' , img ) cv . waitKey ( 0 ) cv . destroyAllWindows () draw4.py
Draw a polygon¶
The polylines function expects a Numpy array for the point list:
pts = [( 50 , fifty ), ( 300 , 190 ), ( 400 , ten )] cv . polylines ( img , np . array ([ pts ]), Truthful , Ruddy , 5 ) 
import cv2 as cv import numpy equally np Red = ( 0 , 0 , 255 ) pts = [( 50 , 50 ), ( 300 , 190 ), ( 400 , 10 )] img = img = np . zeros (( 200 , 500 , 3 ), np . uint8 ) cv . polylines ( img , np . array ([ pts ]), True , RED , 5 ) cv . imshow ( 'window' , img ) cv . waitKey ( 0 ) cv . destroyAllWindows () polygon1.py
Depict a filled polygon¶
The polylines function expects a Numpy array for the point list:
pts = [( 50 , 50 ), ( 300 , 190 ), ( 400 , 10 )] cv . polylines ( img , np . array ([ pts ]), True , Scarlet , v ) 
import cv2 as cv import numpy as np RED = ( 0 , 0 , 255 ) pts = [( 50 , fifty ), ( 300 , 190 ), ( 400 , 10 )] img = img = np . zeros (( 200 , 500 , three ), np . uint8 ) cv . fillPoly ( img , np . array ([ pts ]), RED ) cv . imshow ( 'window' , img ) cv . waitKey ( 0 ) cv . destroyAllWindows () polygon2.py
Describe a polygon with the mouse¶
Combining the previous techniques, it is rather uncomplicated to draw a polygon only by clicking into the window. First nosotros define an empty list:
Each time we click with the mouse we append a point:
def mouse ( upshot , x , y , flags , param ): if event == cv . EVENT_LBUTTONDOWN : pts . append (( x , y )) draw ( 0 ) 
import cv2 every bit cv import numpy as np from draw import * pts = [] def draw ( x ): d = cv . getTrackbarPos ( 'thickness' , 'window' ) d = - 1 if d == 0 else d i = cv . getTrackbarPos ( 'color' , 'window' ) colour = colors [ i ] img [:] = img0 cv . polylines ( img , np . assortment ([ pts ]), True , color , d ) cv . imshow ( 'window' , img ) text = f 'colour= {colour} , thickness= {d} ' cv . displayOverlay ( 'window' , text ) def mouse ( event , x , y , flags , param ): if effect == cv . EVENT_LBUTTONDOWN : pts . append (( 10 , y )) draw ( 0 ) cv . setMouseCallback ( 'window' , mouse ) cv . createTrackbar ( 'colour' , 'window' , 0 , 6 , draw ) cv . createTrackbar ( 'thickness' , 'window' , 2 , 10 , draw ) draw ( 0 ) cv . waitKey ( 0 ) cv . destroyAllWindows () polygon3.py
Draw text¶
import cv2 as cv import numpy as np RED = ( 0 , 0 , 255 ) p0 = ( 10 , 100 ) font = cv . FONT_HERSHEY_SIMPLEX img = np . zeros (( 200 , 500 , three ), np . uint8 ) cv . putText ( img , 'OpenCV' , p0 , font , iv , RED , two , cv . LINE_AA ) cv . imshow ( 'window' , img ) cv . waitKey ( 0 ) cv . destroyAllWindows () text1.py
Reference: https://docs.opencv.org/four.2.0/d6/d6e/group__imgproc__draw.html
Source: https://opencv-tutorial.readthedocs.io/en/latest/draw/draw.html
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